This invention relates to a heat recoverable tubular article which when heated recovers to or toward a specified angle with respect to the axis of the tube and to a method of preparing said article. It further relates to a method of bending an elongate substrate by positioning such a tubular article over the substrate and heating to cause recovery of the article thereby bending the substrate and to the resulting bent substrate.
Wiring and plumbing systems require wires or tubing to be bent at specific angles in specific locations relative to interconnection and "feed-through" points. Common methods of accommodating bends while providing mechanical, electrical, and environmental protection include elastomeric molded parts and heat-shrinkable molded parts.
Elastomeric parts require specialized tooling to fabricate and install, and they are difficult to incorporate in automatic assembly processes. When elastomeric parts are used a part of a connector or conduit assembly, they impart a "rubbery" feel to the connectors, making it difficult to assure the connectors are properly mated. Environmental sealing quality is limited with the "interference fit" method of displacing elastomeric parts. A substrate can be bent using elastomeric "elbow" parts by forcing the substrate through the part or by inserting a straight expandable tool into the part to straighten and enlarge it and then inserting the substrate. Removal of the tool causes the elastomeric elbow to return to its bent shape thus bending the substrate. Angles achieved with elastomeric bending devices are hard to control, as the substrates cause the elastomers to "spring back". Finally, the elastomeric parts are normally "slip fit" to connectors and conduits, and the quality of mechanical fit between the parts provides poor strain relief.
Some limitations of elastomeric molded parts can be overcome with heat-shrinkable molded parts, but heat-shrinkable molded parts also have limitations. A heat-shrinkable part is easier to install, but it is much more difficult to fabricate. In addition, a conventional heat-shrinkable molded part does not have enough force when it is shrinking to bend wire or tubing substrates.
My invention overcomes concerns associated with elastomeric parts while also addressing limitations of conventional heat-shrinkable molded parts.